Hammer.js is a jQuery plugin that gives you multitouch interaction - tapping, double-tapping, pinch and zoom, dragging, and even transform - like rotating - and its pretty cross-platform. If you want to make a web page have native mobile device-like features, this should be on your list to check out.

ckeditor is a great collection of javascript and css that turns a text area into a small word processor. This gem bundles that up as an asset gem so you can use it with one css style on a textarea field.

No, this isn't a duplicate story, this is another gem that packages up ckeditor, but this one also includes stuff for handling image uploads, integration with simple form, and a bunch of other nice stuff thanks to rails engines.

There are many finite state machine implementations for Ruby, and they all provide a nice DSL for declaring events, exceptions, callbacks, and all kinds of niceties in general. But if all you want is a finite state machine, look at Micromachine. Its only 22 lines of code and provides everything a finite state machine must have, and nothing more.

Bogan Gusiev wrote in to tell us about his tool, diffbench. Given a set of performance tests, a patch, and a codebase, it runs the tests both with an without the patch, producing a table with the statistics. You can see it in use on these patches for ActiveRecord, ActiveModel, ActiveSupport, and Mail.